2022 Nobel Prize In Physics Lectures

If you are bored over the holidays, here's something to keep you occupied for 2 hours.

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How Classical Kinetic Energy Is Actually A Subset Of Relativistic Kinetic Energy

Many people think that Classical Physics and Relativistic Physics are two different things. Of course, anyone who has studied both can tell you that one can derive many of the classical physics equations from relativistic equations, proving that classical equations are actually special cases of the more general relativistic equations.

In this Don Lincoln's video, he shows how classical kinetic energy that many students learn in General Physics courses can actually be derived from the more general relativistic energy equation, and why we still use the classical physics equation in most cases.

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Excel Vector Calculator - Be Careful How You Use It

I was asked to show this video to students on how to set up their own vector calculator using Excel. The calculator gives you the ability to find the sum of vectors just by entering each vector's magnitude and direction.

Is it useful? Sure it is, but this is where if you don't know what is going on, you may be using it incorrectly! I have a couple of examples to show that.

After you have set up the calculator using the example shown in the video, enter these:

Vector A: Mag=9.8; Ref. Angle=114

Vector B: Mag=16.5; Ref. Angle= -104

Vector C: Mag=11; Ref. Angle=180

If you have set up the calculator correctly, you will get the resultant vector having a magnitude of 20.2 and a direction of 20.4 degrees.

If you don't know any better and I ask you to sketch out the direction of this vector, you would have drawn an arrow that is pointing in the first quadrant of a Cartesian coordinate system, which would be WRONG! In fact, most of my students would do that. It is a natural and automatic tendency to do so since angles are measured counter clockwise relative to the positive x-axis.

If you do a quick sketch and do a "tip-to-tail" vector addition, you will end up with a vector that is actually pointing in the 3rd quadrant! In fact, the true angular direction for this vector is 200.4 degrees (180 + 20.4, the latter is the angle found from the calculator).

The reason for this is that in calculating the angle, one is dividing the y-component by the x-component. This vector has both components being negative and so the division produces a positive value, producing a positive angle. But this angle given by the calculator, if one were to sketch out the vector, is the angle measured from the NEGATIVE x-axis, not the standard positive x-axis. If one remembers lessons from trigonometry, it is why the value of the tangent of an angle is positive in both the 1st and 3rd quadrant.

So the angle given is "correct" if one knows where it is measured from.

Here's another example to try:

Vector A: Mag=12.7; Ref. Angle=45

Vector B: Mag=19.2; Ref. Angle= -171

Entering this into the calculator, you get the resultant vector having a magnitude of 11.7 and angular direction of -30.9 degrees.

Once again, if you simply go by what you get, the tendency here is to think that the vector is in the 4th quadrant, because a negative angle means that it is an angle measured from the positive x-axis but going clockwise.

This is wrong.

The vector is actually in the 2nd quadrant. A simple sketch to do the vector addition will confirm that. The angle "-30.9 degrees" is actually an angle measured clockwise from the NEGATIVE x-axis. For this vector, the x-component of the resultant is negative, and thus, the ratio of the y-component to the x-component is negative, resulting in a negative value of the tangent and the angle. Once again, from trigonometric lesson, the tangent of an angle is negative in the 2nd and 4th quadrant.

What this all means is that a positive angle value is not unique - the vector could be in the 1st or 3rd quadrant - while a negative angle value is also not unique - the vector could be in the 2nd of 4th quadrant. Either do a quick sketch to do vector addition, or look at the sign of the resulting components.

There are two important lessons here. First is that one must know what the numbers mean. Using them blindly without understanding how they come about is risky and may result in the wrong conclusion. Secondly, for this exercise, there is no substitute for doing a sketch and knowing how vectors add. A simple sketch will provide an important sanity check that your conclusion about the vector direction is not wrong.

While this video and the setting up of the calculator is useful, the producer did not go far enough to demonstrate the possible pitfalls in using it blindly. There should have been examples involving what I had presented to tell the viewers what they should be careful about. I just wonder how many people had used this and interpreted their results incorrectly.

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Quantum Mechanics and the Double-Slit Experiment

The double-slit experiment continues to be of interest with respect to quantum mechanics, even after so many years. I've mentioned about this many times, with this one being the most relevant here to this particular post. And note that I made that blog entry back in 2013!

This time, Don Lincoln of Fermilab has released a video on the topic of the double-slit experiment and how it is relevant to QM.

BTW, has he lost weight? If he has, I hope it is on purpose and not due to an illness.

In any case, watch the video and check out the link that I gave. This issue doesn't look like it will be resolved anytime soon unless some new experiment comes up.

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The Sad Ending of Aricebo Observatory

It was less than a month ago, on a Nov. 19, 2020 report, that the National Science Foundation announced the closure of the famed Aricebo Observatory in Puerto Rico due to structural and safety problems. Unfortunately, on Dec. 1, 2020, the collapse of the central structure happened, with dramatic footage released by the observatory.

While the famed telescope is gone, it will live forever in many footage from movies and tv shows. This is in addition to the numerous scientific discoveries that it has made throughout its operation.

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Roger Penrose - Is Mathematics Invented or Discovered?

 Now that he has just be awarded the 2020 Nobel Prize in Physics .... :)

This is a video of a conversation with Roger Penrose on his opinion of mathematics and its ability to describe our world.

 

Eugene Wigner also had written a rather popular essay on what mathematics is and its "unreasonable effectiveness" in describing our world.

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Quantum Entanglement

I made a post quite a while back on "Quantum Entanglement for Dummies" that tried to describe what it is. I emphasized the fact that this phenomenon is different than classical physics because of one every important characteristics of quantum mechanics, which is the superposition principle that is built into the quantum wavefunction. So to be able to understand why quantum entanglement exists and why it is so "spooky", one must first understand the superposition concept.

Don Lincoln has produced a video on quantum entanglement, and if you pay attention closely, he starts off with describing the superposition concept and how that made a quantum system not "predetermined" before a measurement. He also give a good overview on a Bell-type measurement that shows how experiments agree with QM description but not the hidden variables scenario.



A good video to start you off on understanding this phenomenon.

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What Really Happened At The Big Bang?

Don't you want to know?

Here is a simplified explanation of what the Big Bang is, and what the Big Bang is NOT!



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Tesla Coil at MSI

I was at the Chicago Museum of Science and Industry this past weekend, and got to see the Tesla Coil presentation. I've seen this several times, but it is always a hoot, so we never miss it every time we are there.

Strangely enough, this is the first time I've recorded a video of it, so here it is.



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What Is Quantum Mechanics Really All About?

Don Lincoln tries to explain what QM is to non-expert. Do you understand, and buy it?



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Big Bang Disproved?!

Of course not! But this is still a fun video for you to watch, especially if you are not up to speed on (i) how we know that the universe is expanding and (ii) the current discrepancy in the measurement of the Hubble constant via two different methods.



But unlike politics or social interactions, discrepancies and disagreement in science are actually welcomed and a fundamental aspects of scientific progress. It is how we refine and polish our knowledge into a more accurate form. As Don Lincoln says at the end of the video, scientists love discrepancies. It means that there are more things that we don't know, and more opportunities to learn and discover something new.

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Einstein's Blunder Explained

This, actually, is a good and quick summary of the Einstein cosmological equation by Minute Physics. You'll get a brief history of the cosmological constant, and how it came back to life.



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150 Years of the Periodic Table

Happy 150th Birthday, Periodic Table! You don't look a day over 149!



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How Do You Detect A Neutrino?

Another Don Lincoln video, and this time, it is on a topic that I had a small involvement in, which is neutrino detection.



My small part was in the photomultiplier photocathode used for detection of Cerenkov light that is emitted from such a collision between the "weak boson" and the nucleus. We were trying to design a photodetector that has a large surface area as compared to the current PMT round surface.

In any case, this is a good introduction to why neutrinos are so difficult to detect.

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Why Does Light Bend When It Enters Glass?

Don Lincoln tackles another "everyday" phenomenon. This time, he tries to give you an "explanation" on why light changes direction when it goes from one medium to another, and why some of the more popular explanation that have been given may be either incomplete, or wrong.



Certainly, any undergraduate physics student would have already dealt with the boundary conditions using Maxwell's equations, so this should be entirely new. However, he skipped rather quickly something that I thought was not handled thoroughly.

The continuity of the parallel component of E to the boundary is fine. However, Lincoln argued that the reason why the perpendicular component of the F field is shorter in glass is due to the polarization of the material, and thus, the sum of the light's E-field and the E-field from the polarization will cause the net, resultant E-field to be shorter.

But if the material's polarization can affect the perpendicular component, why doesn't it also affect the parallel component? After all, we assume that the material is isotropic. This, he left out, and at least to me, made it sound that the parallel component is not affected. If this is so, why?

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How Beauty Leads Physics Astray

Sabine Hossenfelder is probably doing a "book tour", since this talk certainly addressed many points that she brought up in her book.



As I've said many times on here, I don't disagree with many things that she brought up. I find the trend of foundational physics to even think about discarding experimental verification to be very troubling. I'm just glad that the field that I'm in is still strongly experimental.

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How Do You Make Neutrino Beam?

This new Don Lincoln's video is related to the one he did previously on the PIP-II upgrade at Fermilab. This time, he tells you how they make neutrino beams at Fermilab.



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PIP-II Upgrade At Fermilab

Don Lincoln explains why the PIP-II upgrade at Fermilab will take the accelerator facility to the next level.



The video actually explains a bit about how particle accelerator works, and the type of improvement that is being planned for.

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Brian Greene on Science, Religion, Hawking, and Trump

I've only found this video recently, even though it is almost a year old already, but it is still interesting, and funny. And strangely enough, he shares my view on religion, especially the fact that people seem to ignore that there are so many of them, each claiming to be the "truth". They all can't be, and thus, the biggest threat and challenge against a religion is the existence of another religion.



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Why Does Light Slow Down In A Material?

Don Lincoln tackles one of those internet/online FAQs. This time, it is an explanation on why light slows down in water, or in matter in general.



Certainly, this is the explanation many of us know when we were in school. However, most of the questions that I get regarding this phenomenon came from people who want to know the explanation at the "quantum" level, i.e. if light is made up of photons, how does one explain this phenomenon in the photon picture? That is the origin of the two "wrong" explanations that he pointed out in the video, i.e. people wanting to use "photons" to explain what is going on here.

Actually, Don Lincoln could have gone a bit further with the explanation and included the fact that this explanation can account for why the speed of light (and index of refraction) inside a material is dependent on the frequency of the light entering the material.

Strangely enough, this actually reminded me of a puzzle that I had when I first encountered this explanation. If the electrons (or the electric dipoles) inside the material oscillate and create an additional EM wave, and the superposition of these two waves give rise to the final wave that appears to move slower in the material, then what stops this second EM wave from leaving the material? Is it only confined within the material? Do we detect "leakage" of this second or any additional wave due to things oscillating in the material? Because the second wave has a different wavelength, it will be refracted differently at the boundary, so it will no longer be aligned with the original wave after they leave the material, if they all leave the material.

Anyone knows?

Edit: Funny enough, and maybe because I watched this video, YouTube gave me an old MinutePhysics video that used the bouncing light particle explanation that Don Lincoln says isn't correct.



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